Nozzle apparatus for burning fuel



R. CALZOLARI NOZZLE APPARATUS FOR BURNING FUEL Oct. 26, 1965 2Sheets-Sheet 1 Filed May 14, 1962 INVENTOR. Foberfo 'Ca/zo/ari W L Oct.26, 1965 R. CALZOLARI 3,213,919

NOZZLE APPARATUS FOR BURNING FUEL Filed May 14, 1962 2 Sheets-Sheet 2INVENTOR. Ro BERTO CALZOLARI WYQM AT TOR NEYS United States Patent F3,213,919 NOZZLE APPARATUS FOR BURNING FUEL Roberto Calzolari, ViaSerpieri 8, Rome, Italy Filed May 14, 1962, Ser. No. 194,641 5 Claims.(Cl. 158-76) This is a continuation-in-part of my prior applicationSerial No. 796,526, filed March 2, 1959, and now abandoned.

This invention relates to an improved fuel burner for burning fuel whichcan be employed to particular advantage in kilns.

Improved heat transfer characteristics are particularly diflicult toobtain in existing furnaces without substantially altering the existingstructure. This is particularly true for furnaces, such as kilns,operating at comparatively low temperatures, wherein substantialimprovement in heat transfer efficiency can only be brought about byimproving convection coefficients. However, by altering t-hecharacteristics of a flame which heats the kiln, it is possible tosubstantially increase the amount of heat transferred by radiation fromthe flame and, consequently, improve the efliciency of the kiln.Radiation from a flame is affected by its temperature, emission factor,and radiant surface. An increased flame temperature will increaseradiation and can be accomplished by providing rapid and thorough mixingof the fuel and air to obtain faster, more intense combustion. A higheremission factor will increase radiation and can be achieved with aluminous flame produced by relatively slow mixing of the fuel with aninsuflicient amount of air. Larger radiant surfaces will increaseradiation and can be achieved by providing a hollow conical flame whichenables a maximum area to be obtained for a given volume of fuel andair.

The new burner for combustion according to the invention increases flameradiation by all three of the above approaches. Rapid mixing and intenseburning is produced in portions of the flame to produce intense heat andhigh temperatures. Slower mixing of the fuel with an insuflicient amountof air is established in other portions of the flame to produceluminescence. A much longer, conical, hollow flame than those heretoforeknown is also produced to provide a larger and more effective radiantsurface. The expression hollow flame as used herein denotes a flamewhich is defined between two co-axial conical surfaces which haveslightly different angles of generation, with the lateral cross sectionof the flame constituting an annulus.

The burner according to the invention produces a flame which is shapedbetween a conventional solid flame and a conventional shallow, conicalflame produced by whirling burning products of combustion. Inaccomplishing this, the new flame also combines high heat intensity andhigh luminescence, either of which can be obtained singularly with thefirst flame, with the large surface area of the second flame. Theimproved flame also corresponds more closely to the shape of the kiln orother chamber into which the flame is emitted and can be directed closerto the object or material intended to be heated than can be the shallow,whirling flame.

The new flame is produced by dividing fuel, preferably oil, into anumber of entirely separate streams which are given a slight twist toproduce both an axial and a tangential component of movement. Theindividual streams are then forced through an annular, tapered passageof decreasing dimensions to substantially increase the axial velocitywithout substantially affecting the tangential velocity. The annularpassage causes the fuel passing therethrough to rotate more rapidly nearthe inner surface of the passage than near the outer surface 3,213,919Patented 0st. 26, 1965 with the result that the fuel particles in eachstream tend to be separated but, nevertheless, the individual streams donot initially tend to mix together. The size and number of the streamsare proportioned in such a manner that the particles produce a vapor ofsmall drops which vary in diameter but are uniformly distributed withinthe streams and within a space defined between two coaxial conicalsurfaces outside the burner, after the streams are forced through theannular passage. By varying the number of streams and their tangentialcomponents within certain limits, it is possible to adapt the shape ofthe flame to that of the particular enclosed space in which it isutilized.

Both an inner cylindrical stream and an annular outer stream of primaryair are directed concentrically around the paths of the fuel oilstreams. The inner primary air stream is caused to travel at lowervelocity than the outer primary air stream so that mixing of the fueland inner primary air is relatively slower. Further, the quantity of airin the inner stream is insuflicient to produce complete combustion.Consequently, a long, luminous flame with high emissivity is producedinitially. Rapid mixing of the outer, annular primary air stream andunburned portions of the fuel streams subsequently occurs, resulting inrapid and intense burning and high heat intensity. The remainingportions of the fuel streams finally are burned with secondary, heatedair in the kiln. The quantity of air in the inner primary air stream canalso be varied to control the extent of initial combustion and therebycontrol the effective length of the flame.

It is, therefore, a principal object of the invention to provide a flamecapable of more rapidly transmitting heat, principally by radiation.

Another object of the invention is to provide a flame having high heatintensity, high emissivity, and a large surface area.

Still another object of the invention is to provide a conical flamewhich is longer and more narrow than those heretofore known.

A further object of the invention is to provide a burner which iscapable of producing a flame having the characteristics and advantagesdiscussed above.

Still a further object of the invention is to provide a burner fromwhich fuel is emitted in a plurality of separate streams defining acone, with primary air supplied therearound in cylindrical and annularpaths, and with means for varying the quantity of air in the cylindricalstream to thereby vary flame length.

Other objects and advantages of the invention will be apparent from thefollowing detailed description of a preferred embodiment thereof,reference being made to the accompanying drawing, in which:

FIG. 1 is a view in cross section showing a burner according to theinvention, including means for controlling the flow of primary air;

FIG. 2 is a greatly enlarged view in cross section showing the detailsof the burner nozzle; and

FIG. 3 is a further enlarged, fragmentary view, with parts broken awayand with parts in cross section, of a nozzle similar to that of FIG. 2.

Referring more particularly to FIGURE 1, a burner according to theinvention is indicated at 10 and includes a duct 12 and a relatively lowpressure blower 14 of conventional design. A venturi tube 16 isconcentrically located in the duct 12 by means of spiders 18 and a fuelline 20 extends axially through the tube 16 and through the back of theblower housing 14, being supported by a hangar 22 afiixed to an upperportion of the venturi tube 16. The line 20 is connected to any suitablesource of fuel oil. A double conical valve member 24 consisting of twocones 26 and 28 and a sleeve 30 is slidably supported on the fuel line20 and extends through the back of the blower housing 14 to a flange orhandle 32. The surface of the cone 28 has the same angle of generationas the inner surface of the entrance of the venturi tube 16 tocompletely close off the entrance when the member 24 is slid to itsforward position. Axial movement of the member 24 varies the annularentrance of the venturi tube 16 and thus varies the amount of airflowing through the venturi tube 16 and to some extent the amount of airflowing through an annulus 17 between the tube 16 and the duct 12.

A nozzle 34 located at the front end of the fuel line 20 is shown indetail in FIG. 2 and includes a threaded connector 36 which connects ahousing 38 to the fuel line 20. The connector is screwed into a recess40 in the housing 38, against a gasket 42, and has a passage 44 alignedwith a passage 46 in a core 48. A flange 50 concentrically locates therear portion of the core 48 with respect to a cylindrical inner surface52 of the housing 38. A small shank 54 forming part of the core 48connects the flange 50 with a segment 56 which has a plurality ofhelical ridges 58 thereon forming helical channels 60 therebetween. Atthe downstream end of the segment 56 is a blunt cone 62 which extendsinto a conical recess 64 of a nozzle member 66. The cone 62 has aslightly steeper angle of taper than the conical recess 64 which therebyform a conical, annular passage decreasing in both diameter andthickness from the segment 56 to an orifice 68 at the extremity of themember 66. A flange 70 supports the member 66 concentrically withrespect to the inner surface 52 of the housing 38 and positions theorifice 68 and the recess 64 concentrically with respect to the cone 62.A gasket 72 is nested between the flange 70 of the member 66 and aflange 74 of the housing 38 to maintain a tight connection therebetween.A spacer 76 properly longitudinally spaces the cone 62 of the core 48from the conical recess 64 of the nozzle member 66 and also defines anannular manifold 78 between its inner surface and the shank 54. Aplurality of ports 80 connect the annular manifold 78 With the passage46.

Fuel from the line is supplied under pressure through the passage 44,into the passage 46, through the ports 80, and into the annular manifold78. From here, it is divided into separate streams by the separatehelical channels 60 formed between the helical ridges 58, the segment56, and the inner surface of the spacer 76. The streams then flowthrough the tapered, narrowing passage between the cone 62 and theconical recess 64 where the axial velocity is greatly increased but thetangential velocity is affected to a much lesser extent. Those portionsof each stream near the inner surface of the conical passage tend toflow more rapidly than those portions near the outer surface with theresult that the particles in each stream tend to be pulled apart butstill stay within their respective streams. This differential effect onthe various particles produces a predisposition to atomization whichtakes place rapidly when the high velocity streams impact the relativelystationary air outside the orifice 68. The streams are emitted from theorifice 68 in diverging paths producing an overall conical shape andcontinue outwardly until they meet the primary air.

In accordance with the present invention, the primary air is supplied inan inner cylindrical stream, indicated by the short arrows in FIG. 1,through the tube 16, and in an outer annular stream indicated by thelong arrows, from the annulus 17 between the tube 16 and the duct 12.The air for both of these primary air streams is supplied by the blower14, and the relationships between the entrance and discharge ends of theprimary air passages are so made that the air in the duct 12 is expandeddown to a lower pressure and velocity while the air from the annulus 12is discharged at full pressure and high velocity.

Burning of the fuel streams first occurs at the intersection of the fuelstreams and the inner, primary air stream, and this burning isrelatively slow because the velocity of the primary air is relativelylow and the quantity of air in this stream is insufficient to completethe combustion of even a major portion of the fuel. Therefore, a longluminous flame is produced initially. However, at the area ofintersection of the fuel streams and the outer annular primary airstream, more rapid and intense burning occurs because of rapid mixing ofthe fuel with the high velocity outer annular primary air stream.Completion of the combustion of the fuel streams takes place within thekiln with secondary air which is induced in a heated condition.

The particular form of emission of the fuel from the nozzle 34 enablesthe flame to have a long, hollow, conical shape, much. longer and morenarrow than a conventional whirling flame with a relatively shallowangle and a relatively short length. The new flame enables a substantialradiating surface to be obtained and yet enables the burning gases to bedirected closer to the objects or materials to be heated. Thus, in mostinstances, the source of radiation is closer to the object or materialsthan is a conventional whirling flame. Furthermore, the length of thenew flame can be easily changed by varying the quantity of air containedin the inner primary air stream and admitted through the tube 16 andthereby control the extent and rate of initial combustion.

The quantity of air admitted in the inner primary air stream can bechanged by changing the position of the member 24 on its supporting pipe20. If the member is moved back to increase the volume of air in theinner stream the flame becomes shorter, and if the member is movedforwardly to reduce the volume of air in the inner stream by throttlingthe intake end of the passage formed by the tube 16 the length of theflame will increase.

A slightly modified nozzle 82 is shown in FIG. 3. This nozzle issubstantially similar to that of FIGS. 1 and 2 except that a core 84 hasridges extending in the opposite direction to those of FIG. 2 and a cone86 has a concave, blunt end which is preferred to a truly truncated one.A nozzle member 88 also differs slightly from the member 66 because themember 88 has a shallow end recess 90.

For both the nozzles 34 and 82, the angle A of the blunt cone will varyfrom 15 to 21 while the angle B of the recess 64 will vary from 19 to25, being more than the angle A of the cone. In addition, the ratio ofthe product of the diameter D of the large end of the recess and thediameter E of the small end of the cone to the product of the diameter Cof the large end of the cone and the diameter F of the small end of therecess will exceed 1.0 and will not exceed 1.36. Expressed as anequation:

The value for K will depend on the metal employed in the nozzleelements, the surface obtained on the cone, and, to some extent, on theviscosity of fuel oil used. Fuel pressures employed vary from 13 to 40kilograms per square centimeter.

In practice, the required nozzle area is determined by:

is first calculated, based on output desired and pressures available.The diameters C and D can then be found and the length of the cone andrecess subsequently determined so that the angles of them will fallwithin the aforementioned ranges.

The recess in the blunt end of the cone has a radius R equal to 1.5 F.

While the blunt end of the cone 86 is recessed, and the blunt end of thecone 62 is shown as truncated, other configurations of the blunt end maybe used. It is important that the surface of the cone deviate inwardlyat a point immediately upstream of the orifice 68 so that the stream offuel oil separates from the surface of the cone near the beginning ofthe deviation.

While the above discussion and accompanying drawings have discussed andillustrated only one specific form of the invention, it is to beunderstood that this form has been shown for purposes of illustrationand is not employed in a limiting sense. Consequently, it is to beunderstood that various modifications can be embodied in the inventionwithout departing from the scope of the claims appended hereto.

What I claim is:

1. A nozzle for a liquid fuel burner for producing a high temperatureflame with high emissivity and a large radiant surface, said nozzleincluding a nozzle member having a conical recess at a downstream endthereof, the included angle of said recess being constant throughout thelength of said recess and ranging from 19 to 25, a core having atruncated cone forming an angle which is constant throughout the lengthof said cone and ranges from 15 to 21, said cone extending into saidrecess to form an annular passage decreasing in diameter at a uniformrate, said member forming a cylindrical passage located immediatelybeyond a smaller, blunt end of said cone and co-axial therewith, meansfor maintaining said member and said core in fixed, spaced relationship,a plurality of helical ridges on said core forming a plurality ofseparated helical passages with a portion of said spacing means, meansforming a manifold in said nozzle member upstream of said helicalpassages, and means for supplying fuel under pressure to said manifold.

2. A nozzle for a fuel oil burner for producing a high temperature flamewith high emissivity and a large radiant surface, said nozzle includingnozzle means forming a conical recess at the downstream end thereof,said conical recess having a large end and a small end, and forming anincluded angle which is constant throughout the length of said recessand ranges from 19 to 25, a core having a truncated cone with a largeend and a small end, with a steeper angle of taper than the angle ofsaid conical recess, said cone angle being constant throughout thelength of said cone and ranging from 15 to 21, with the product of thediameters of the large end of said recess and the small said of saidcone exceeding the product of the diameters of the large end of saidcone and the small end of said recess, said cone extending into saidrecess, said nozzle means forming a cylindrical passage beyond thesmall, blunt end of said cone and located coaxially therewith, aplurality of helical ridges on said core forming a plurality ofseparated helical passages with a portion of an inner surface of saidnozzle means, and means for supplying fuel under pressure to saidhelical passages.

3. A nozzle according to claim 2 wherein the first product exceeds thesecond product by a factor of not more than 1.36.

4. A nozzle for a liquid fuel burner for producing a high temperatureflame with high emissivity and a large radiant surface, said nozzleincluding a nozzle member having 'a conical recess at a downstream endthereof, a core having a cone extending into said recess to form anannular passage therewith decreasing in diameter at a uniform rate, saidmember forming a cylindrical orifice located immediately beyond a smallend of said cone and being co-axial therewith, the small end of saidcone being blunt with the conical surface of the cone deviatinginwardly, and forming a recess immediately upstream of said orificewhereby liquid fuel flowing contiguously to the surface of said conewill separate therefrom at the devitation of the surface, said recesshaving a radius exceeding the diameter of the small end of said cone andextending completely to the conical surface at the small end of saidcone, means for maintaining said member and said core in fixed, spacedrelationship, a plurality of helical ridges on said core forming aplurality of separated helical passages with a portion of said spacingmeans, means forming a manifold in said nozzle member upstream of saidhelical passages, and means for supplying fuel under pressure to saidmanifold.

5. A nozzle for a liquid fuel burner for producing a high temperatureflame with high emissivity and a large radiant surface, said nozzleincluding a nozzle member having a conical recess at a downstream endthereof, the included angle of said recess being constant throughout thelength of said recess and ranging from 19 to 25 a core having a coneforming an angle which is constant throughout the length of said coneand ranges from 15 to 21, said cone extending into said recess to forman annular passage therewith, said member forming a cylindrical orificelocated immediately beyond a small end of said cone and being co-axialtherewith, the small end of said cone being blunt with the conicalsurface of the cone deviating inwardly immediately upstream of saidorifice whereby liquid fuel flowing contiguously to .the surface of saidcone will separate therefrom at the deviation of the surface, means formaintaining said member and said core in fixed, spaced relationship, aplurality of helical ridges on said core forming a plurality ofseparated helical passages with a portion of said spacing means, meansforming a manifold in said nozzle member upstream of said helicalpassages, and means for supplying fuel under pressure to said manifold.

References Cited by the Examiner UNITED STATES PATENTS 391,865 10/88Schutte 158-78 1,089,406 3/41 Fitts 239-488 1,319,527 10/19 Kreuzhage239488 1,810,689 6/31 Townsend et a1. 239488 FOREIGN PATENTS 829,6831/52 Germany.

JAMES W. WESTHAVER, Primary Examiner.

PERCY L. PATRICK, MEYER PERLIN, Examiners.

1. A NOZZLE FOR A LIQUID FUEL BURNER FOR PRODUCING A HIGH TEMPERATUREFLAME WITH HIGH EMISSIVITY AND A LARGE RADIANT SURFACE, SAID NOZZLEINCLUDING A NOZZLE MEMBER HAVING A CONICAL RECESS AT A DOWNSTREAM ENDTHEREOF, THE INCLUDED ANGLE OF SAID RECESS BEING CONSTANT THROUGHOUT THELENGTH OF SAID RECESS AND RANGING FROM 19* TO 25*, A CORE HAVING ATRUNCATED CONE FORMING AN ANGLE WHICH IS CONSTANT THROUGHOUT THE LENGTHOF SAID CONE AND RANGES FROM 15* TO 21*, SAID CONE EXTENDING INTO SAIDRECESS TO FORM AN ANNULAR PASSAGE DECREASING IN DIAMETER AT A UNIFORMRATE, SAID MEMBER FORMING A CYLINDRICAL PASSAGE LOCATED IMMEDIATELYBEYOND A SMALLER, BLUNT END OF SAID CONE AND CO-AXIAL THEREWITH, MEANSFOR MAINTAINING SAID MEMBER AND SAID CORE IN FIXED, SPACED RELATIONSHIP,A PLURALITY OF HELICAL RIDGES ON SAID CORE FORMING A PLURALITY OFSEPARATED HELICAL PASSAGES WITH A PORTION OF SAID SPACING MEANS, MEANSFORMING A MANIFOLD IN SAID NOZZLE MEMBER UPSTREAM OF SAID HELICALPASSAGES, AND MEANS FOR SUPPLYING FUEL UNDER PRESSURE TO SAID MANIFOLD.